Fiberboard containers for storing bulk products, such as dry-flowable granules, pellets, powders, flakes and the like, exist in various configurations. These containers are typically rated to contain a certain weight of product in a particular stacked configuration. For example, they may be rated to contain 1,000 pounds of product stacked three high. To adequately provide product containment and protection during product storage and shipment in the rated configuration, conventional fiberboard bulk containers are constructed of multiple layers of heavy papers combined in a laminated fiberboard construction. Typically, the compression strength of these containers for a given rating equals 5.3 to 7 times the anticipated weight stacked on top of the container. This high compression strength is needed to account for the effects of time under load (structure fatigue) and humidity (moisture strength degradation). For instance, a typical container expected to hold 1,500 lbs of product stacked three containers high would require a compression strength of approximately 17,000 to 22,400 lbs. depending on the severity of humidity and length of time in storage (including carton weight and pallet weight of about 100 pounds per container). The heavy papers of these conventional containers add significant expense to cost of the cartons.
Further, conventional cartons fail to adequately resist bulging over time due to the free-flowing nature of the bulk products contained therein. This is because dry-flowable materials stored within a carton exert an outward pressure on the carton walls that increases toward the bottom of the carton, much like hydrostatic pressure increases with depth within a fluid container. This encourages the carton walls to bulge when overstacked or upon degradation, such as from extended exposure to humidity. Conventional fiberboard cartons absorb moisture over time from humidity, which degrades the top-to-bottom compression strength of their sidewalls as well as their resistance to bending. As such, they tend to bulge over time in humid environments.
Accordingly, a need exists for a bulk materials fiberboard container that has high compression strength, resists bulging and withstands degradation due to humidity. Further, a need exists for a bulk materials fiberboard container that uses less fiberboard material than conventional containers.
Containers have been proposed for addressing one or more of these needs. U.S. Pat. No. 5,772,108 to Ruggiere, Sr. et al. (Ruggiere) discloses a corrugated paperboard container having reinforcement straps. The reinforcement straps are prestretched polypropylene straps placed about the girth of the carton in the flattened condition, which resist carton bulging in the erect, filled condition. The reinforcement straps permit double-wall containers to be double stacked during product storage. The reinforcement straps of Ruggiere provide concentrated reinforcement at their locations along the girth of the carton, but fail to provide reinforcement along the span of the vertical walls. Ruggiere also teaches applying a moisture-resistant coating to the paperboard to resist deterioration from water offsets. However, the moisture-resistant coating of Ruggiere is in addition to the reinforcement straps, which adds expense to the carton beyond expenses related to the cost of the reinforcement straps.
U.S. Pat. No. 5,515,662 to Johnstone (Johnstone) discloses a bulk package having a pair of reinforcing stretch film straps wrapped perpendicular to each other to form a cross pattern around a container, which is constructed of plastic film. One of the straps, which is wrapped around the top and bottom of the carton, also wraps around rigid spacer members to permit engagement with forks of a lift vehicle. Because the cartons are formed from plastic film, they lack compression strength on their own beyond the compression strength of the bulk materials stored therein.
In addition to such proposals, bundling of multiple packages together on a pallet or base is known for improving the shippabililty of the cartons. For example, U.S. Pat. No. 3,852,937 to Bitsura et al. (Bitsura) discloses a method for shrink-wrapping objects arranged on a pallet or base. In particular, Bitsura shows a method for shrink-wrapping a tubular sheet of polyethylene film around objects arranged on a base such that the sheet wraps around the base. However, the method of Bitsura does not provide reinforcement to individual cartons. It further requires the application of heat to accomplish shrink-wrapping, which adds expense and complexity to the process.
As discussed above, a need still exists for an improved bulk materials fiberboard container that has high compression strength, resists bulging, and withstands degradation due to humidity. Further, a need exists for such an improved bulk materials fiberboard container that saves cost by using less fiberboard material than conventional containers.